<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://unpkg.com/vue/dist/vue.js"></script>
    <script src="https://unpkg.com/vue-router/dist/vue-router.js"></script>
</head>
<body>
<div id="app">
    <p>
        <router-link to="/user/foo">/user/foo</router-link>
        <router-link to="/user/foo/profile">/user/foo/profile</router-link>
        <router-link to="/user/foo/posts">/user/foo/posts</router-link>
    </p>
    <router-view></router-view>
</div>
<script>
    const User = {
        template: `
    <div class="user">
      <h2>User {{ $route.params.id }}</h2>
      <router-view></router-view>
    </div>
  `
    }

    const UserHome = { template: '<div>Home</div>' }
    const UserProfile = { template: '<div>Profile</div>' }
    const UserPosts = { template: '<div>Posts</div>' }

    const router = new VueRouter({
        routes: [
            { path: '/user/:id', component: User,
                children: [
                    // UserHome will be rendered inside User's <router-view>
                    // when /user/:id is matched
                    { path: '', component: UserHome },

                    // UserProfile will be rendered inside User's <router-view>
                    // when /user/:id/profile is matched
                    { path: 'profile', component: UserProfile,beforeEnter: (to, from, next) => {
                        alert('profile')
                        next()
                    } },

                    // UserPosts will be rendered inside User's <router-view>
                    // when /user/:id/posts is matched
                    { path: 'posts', component: UserPosts,beforeEnter: (to, from, next) => {
                        alert('posts')
                        next()
                    } }
                ]
            }
        ]
    })

    const app = new Vue({ router }).$mount('#app')
</script>
</body>
</html>